×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

drooling nylon

drooling nylon

drooling nylon

(OP)
why does nylon tend to drool? Is it do to crystallinity? Does an amorphous nylon drool less?

RE: drooling nylon

The question you ask is a bit bigger that i think you expect, but basically, nylon normally has a low melt viscosity and a very sudden transition from solid to liquid. Amorphous nylons tend to be less sudden.

Also nylon is hygroscopic, and if it has absorbed much water, then the outguessing as the water boils off will force some material out the nozzle as drool. If it is moisture causing the drool, the drool will spit and bubble with gas (steam) discharging from the melt.

Bottom line answer.

Ensure the granules are dry.
Ensure the nozzle heater is in good condition, is in good contact with the nozzle (good clean smooth mating surface).
Ensure the heater is very close to the tip of the nozzle.
Use a variable voltage controller to the nozzle, NOT AN ON OFF cycling type controller. DME controllers or even domestic light dimmer switches all work OK.

The temperature fluctuation during reaction times with on off type controllers is enough to cause drool then freeze then drool then freeze cycles to be set up.

Regards
pat   pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: drooling nylon

you can also use a shut-off nozzle to control the drool. This does restrict flow somewhat.

RE: drooling nylon

Make sure you are using a nylon type nozzle, it helps. Crystaline nylon is naturally low in viscosity. Millions of pounds of nylon have been run for 60 years, so this is a managable problem.

RE: drooling nylon

This sounds like a heat issue not a material.

I would ask how you are controlling your heat dissipation to the sprue.  If you have to much contact from sprue to mold or not enough this can cause the sprue to freeze, drool and many other symptoms.

Some presses have the ability to vacuum the nozzle to prevent drool.  I am not really clear on this, but can check with my molding floor to verify.

Cheers

Terry Ables
Micro Plastics Inc.
www.microplastics.com

RE: drooling nylon

It is both a heat and material issue as normally the material nylon has a very sudden transition from solid to a relatively free flowing liquid, and therefore, is exceptionally sensitive to very small changes in temperature at the nozzle, therefore the temperature needs to be very accurately and consistently controlled, buy techniques I previously described.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources